Hello,
I am completely new to Unreal engine, i made my first project (blank game, blueprint, starter tools), and the project consists just from some white landscape, and a red text in the upper left corner says: “LANDSCAPE: 64 ACTORS WITH PHYSICAL MATERIALS NEED TO BE REBUILT”, i found a similar forum post here, tried to do what the people replying to it said, like “Build → Build physical materials only”, or “Build → Build landscape”. Image